/* This is free and unencumbered software released into the public domain. */
#ifndef SKIPJACK_H
#define SKIPJACK_H

static void
skipjack_encrypt(const void *key, void *block)
{
    static const unsigned char f[] = {
        0xa3, 0xd7, 0x09, 0x83, 0xf8, 0x48, 0xf6, 0xf4,
        0xb3, 0x21, 0x15, 0x78, 0x99, 0xb1, 0xaf, 0xf9,
        0xe7, 0x2d, 0x4d, 0x8a, 0xce, 0x4c, 0xca, 0x2e,
        0x52, 0x95, 0xd9, 0x1e, 0x4e, 0x38, 0x44, 0x28,
        0x0a, 0xdf, 0x02, 0xa0, 0x17, 0xf1, 0x60, 0x68,
        0x12, 0xb7, 0x7a, 0xc3, 0xe9, 0xfa, 0x3d, 0x53,
        0x96, 0x84, 0x6b, 0xba, 0xf2, 0x63, 0x9a, 0x19,
        0x7c, 0xae, 0xe5, 0xf5, 0xf7, 0x16, 0x6a, 0xa2,
        0x39, 0xb6, 0x7b, 0x0f, 0xc1, 0x93, 0x81, 0x1b,
        0xee, 0xb4, 0x1a, 0xea, 0xd0, 0x91, 0x2f, 0xb8,
        0x55, 0xb9, 0xda, 0x85, 0x3f, 0x41, 0xbf, 0xe0,
        0x5a, 0x58, 0x80, 0x5f, 0x66, 0x0b, 0xd8, 0x90,
        0x35, 0xd5, 0xc0, 0xa7, 0x33, 0x06, 0x65, 0x69,
        0x45, 0x00, 0x94, 0x56, 0x6d, 0x98, 0x9b, 0x76,
        0x97, 0xfc, 0xb2, 0xc2, 0xb0, 0xfe, 0xdb, 0x20,
        0xe1, 0xeb, 0xd6, 0xe4, 0xdd, 0x47, 0x4a, 0x1d,
        0x42, 0xed, 0x9e, 0x6e, 0x49, 0x3c, 0xcd, 0x43,
        0x27, 0xd2, 0x07, 0xd4, 0xde, 0xc7, 0x67, 0x18,
        0x89, 0xcb, 0x30, 0x1f, 0x8d, 0xc6, 0x8f, 0xaa,
        0xc8, 0x74, 0xdc, 0xc9, 0x5d, 0x5c, 0x31, 0xa4,
        0x70, 0x88, 0x61, 0x2c, 0x9f, 0x0d, 0x2b, 0x87,
        0x50, 0x82, 0x54, 0x64, 0x26, 0x7d, 0x03, 0x40,
        0x34, 0x4b, 0x1c, 0x73, 0xd1, 0xc4, 0xfd, 0x3b,
        0xcc, 0xfb, 0x7f, 0xab, 0xe6, 0x3e, 0x5b, 0xa5,
        0xad, 0x04, 0x23, 0x9c, 0x14, 0x51, 0x22, 0xf0,
        0x29, 0x79, 0x71, 0x7e, 0xff, 0x8c, 0x0e, 0xe2,
        0x0c, 0xef, 0xbc, 0x72, 0x75, 0x6f, 0x37, 0xa1,
        0xec, 0xd3, 0x8e, 0x62, 0x8b, 0x86, 0x10, 0xe8,
        0x08, 0x77, 0x11, 0xbe, 0x92, 0x4f, 0x24, 0xc5,
        0x32, 0x36, 0x9d, 0xcf, 0xf3, 0xa6, 0xbb, 0xac,
        0x5e, 0x6c, 0xa9, 0x13, 0x57, 0x25, 0xb5, 0xe3,
        0xbd, 0xa8, 0x3a, 0x01, 0x05, 0x59, 0x2a, 0x46
    };
    const unsigned char *k = key;
    unsigned char *b = block;
    unsigned i, x, h, l, w[4];
    w[0] = (unsigned)b[1] | (unsigned)b[0] << 8;
    w[1] = (unsigned)b[3] | (unsigned)b[2] << 8;
    w[2] = (unsigned)b[5] | (unsigned)b[4] << 8;
    w[3] = (unsigned)b[7] | (unsigned)b[6] << 8;
    for (i = 0; i < 32; i++) {
        switch (i / 8 % 2) {
        case 0: h = w[0] >> 8;
                l = w[0] & 0xff;
                h ^= f[k[(4*i+0)%10] ^ l];
                l ^= f[k[(4*i+1)%10] ^ h];
                h ^= f[k[(4*i+2)%10] ^ l];
                l ^= f[k[(4*i+3)%10] ^ h];
                w[0] = w[3] ^ (i + 1);
                w[3] = w[2];
                w[2] = w[1];
                w[1] = h<<8 | l;
                w[0] ^= w[1];
                break;
        case 1: x = w[0];
                h = w[0] >> 8;
                l = w[0] & 0xff;
                w[0] = w[3];
                w[3] = w[2];
                w[2] = x ^ w[1] ^ (i + 1);
                h ^= f[k[(4*i+0)%10] ^ l];
                l ^= f[k[(4*i+1)%10] ^ h];
                h ^= f[k[(4*i+2)%10] ^ l];
                l ^= f[k[(4*i+3)%10] ^ h];
                w[1] = h<<8 | l;
        }
    }
    b[0] = w[0] >> 8; b[1] = w[0] >> 0;
    b[2] = w[1] >> 8; b[3] = w[1] >> 0;
    b[4] = w[2] >> 8; b[5] = w[2] >> 0;
    b[6] = w[3] >> 8; b[7] = w[3] >> 0;
}

#endif
